Find the molecular mass of table sugar

Problem

Find the molecular mass of table sugar (sucrose), which has a molecular formula C₁₂H₂₂O₁₁.

Solution

To find the molecular mass, add the atomic masses of all of the atoms in the molecule. Find the atomic mass for each element by using the mass given in the Periodic Table. Multiply the subscript (number of atoms) times the atomic mass of that element and add the masses of all of the elements in the molecule to get the molecular mass. If we round off the atomic masses to four significant figures, we get:

molecular mass C₁₂H₂₂O₁₁ = 12(12.01) + 22(1.008) + 11(16.00) = 342.30

Answer

342.30

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The mass of 2.5 x 10⁹ molecules of H₂O is 7.5 x 10^-14 g.